VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Model Specific > RV-8/8A
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #21  
Old 06-10-2016, 05:03 PM
Bill Palmer Bill Palmer is offline
 
Join Date: Apr 2006
Location: Chino Hills, CA
Posts: 385
Default Alts & Batts

I believe all Robert is saying is that it is always preferable to have a good battery online from an electronics standpoint.

I personally think it’s a great idea to test dual-alternator, single battery systems to see what happens when the battery is removed from a running system. On the other hand, before testing, I would certainly want to research and understand what will probably happen first. Prior analysis and data predictions are good! Smoke is bad!

I also think it’s a great idea (Walt!) to have a small backup battery lurking in the background which the pilot can switch-in, if needed, to power electronics and also help damp the alternator output (. . . essentially, another form of dual-alternator, dual-battery). The capacitors are a great move, too. Are those “flux capacitors,” Walt?! (re: “Back to the Future”)

What is still unclear to me, and maybe someone here can help me with this, is how the B&C linear regulator might, or might not, help mitigate alternator-only output. I have a corresponding email into B&C on this, but does anyone know the answer up-front? From the B&C literature, it is clear that the regulator itself does not generate any noise, but it also appears that noise problems must be discovered and solved at the source rather than via the regulator, including switching off the alternator(s) as a test.

Thanks,
__________________
Bill Palmer
Chino Hills, CA
Reply With Quote
  #22  
Old 06-10-2016, 05:06 PM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 7,122
Default

Quote:
I've tested this very situation in my aircraft with dual alternators and a single battery. I took the battery offline by switching off the master contactor, to test whether the alternator(s) would continue providing power. The result was, if the main alternator field is already energized when the battery goes down, then it continues providing power.
Same test here, with a single Plane Power. Initially I had the same result, but it dropped off line a short time later.

Recall I've also reported a charging failure due to a poor field plug connection. Perhaps dropping off line and the later plug failure are related. With both internal and external regulators, self-excitement of an alternator set up for aircraft requires a current path from B-lead to main bus, then back to the field terminal, via terminals, crimps, breakers, and switches. Without a battery feed, just the slightest momentary interruption anywhere in the circuit causes the alternator to quit.

Yes, alternators should maintain output without an external battery, but maybe it's not a bulletproof assumption.
__________________
Dan Horton
RV-8 SS
Barrett IO-390

Last edited by DanH : 06-10-2016 at 09:44 PM. Reason: Thought about it.
Reply With Quote
  #23  
Old 06-11-2016, 04:03 AM
maniago's Avatar
maniago maniago is offline
 
Join Date: Aug 2014
Location: Bowie MD
Posts: 320
Default I dont get it

Can someone explain to me why you would be flying along, your battery fails (not exactly sure what everyone is defining as a flying battery failure in the first place), and you switch it out of the circuit?

IOW, why would you take the batt off line?

If its gone flat, its still acting as a capacitor and smoothing any ac ripple.

If you got a fire, then all your electricity gets shut down, and your motor flies on pmag or magneto.

What am I missing in the discussion here?
__________________
Mani
Bushby Mustang II (building); IO-360B1E, C2YR-BF/F7666-2
Don't be a hater; I'm a cousin with thin wings!
N251Y (res)
Dec2016
Reply With Quote
  #24  
Old 06-11-2016, 05:45 AM
bret's Avatar
bret bret is offline
 
Join Date: Feb 2010
Location: Gardnerville Nv.
Posts: 2,595
Default

If single batt and alt, and from vibration or what ever, a battery plate opens, then you are reliant on the alternator to keep the power flowing, if for a second in this condition, there is any disruption in power to the field, the power flow stops and that is bad for an electric dependent aircraft, I will have main, backup and Dynon back up batteries. (4 total)
__________________
7A Slider, EFII Angle 360, CS, SJ.
2017 gladly supported
Reply With Quote
  #25  
Old 06-11-2016, 06:42 AM
f1rocket's Avatar
f1rocket f1rocket is offline
 
Join Date: Jan 2005
Location: Martinsville, IN
Posts: 2,256
Default

I've actually built airplanes with both electrical systems. Rocket one was one battery with dual alternators. Rocket two was two batteries with one alternator.

I used a battery management device used in the boating industry to handle the charging.

My vote is two batteries and one alternator. Less components, less cost, less complexity, and more reliability. It's been said already, nothing more reliable than a well maintained battery, and more than enough power to make an alternator failure a non-event.

Just my $.02.
__________________
Randy Pflanzer
Martinsville, IN (II87)

www.pflanzer-aviation.com
Paid through 2043!
Lund fishing Boat, 2017, GONE FISHING
RV-12 - Completed 2014, Sold
427 Shelby Cobra - Completed 2012, Sold
F1 EVO - partially completed, Sold
F1 Rocket - Completed 2005, Sold
RV-7A - Partially completed, Sold
RV-6 - Completed 2000, Sold
Long-EZ - Completed 1987, Sold

Reply With Quote
  #26  
Old 06-11-2016, 07:32 AM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 7,122
Default

Quote:
Originally Posted by maniago View Post
If you got a fire, then all your electricity gets shut down, and your motor flies on pmag or magneto.

What am I missing in the discussion here?
The condition stated in the original question...with all electric fuel pumps and ignitions. The ability to open the master contactor without affecting engine operation is a key system test.

The KIS approach to that condition is to wire the ignitions and pumps directly to battery feeds which have no dependence on the aircraft electrical system.

Basic VFR and IFR architecture:



I'll submit three principles, often overlooked while designing grand electrical schemes with many wonderful features.

1. Any pilot should be able to operate it without instruction. Put another way, operation should be self-evident, or the same as any other airplane.

2. The battery feeds should be physically separated from the rest of the wiring, to the maximum extent possible. They should also be separated from each other.

3. The least complex system is usually the most reliable.

Humor a bit of editorializing.

Right now, we're growing a fleet with no electrical commonality. At the same time, we're bringing in more and more non-builder pilots from the traditional GA fleet. E-busses, cross feeds, and switch flipping to maintain engine noise is a recipe for increased accident numbers. Time and time again, the human factor is the stubborn cause we can't make go away.

Physical separation is important. We see a nice wiring diagram intended to isolate problems, but then the builder installs the backup alongside the primary. Doing so makes them subject to the same physical trauma, whatever it might be, and one can take out the other.

As for the least complex being the most reliable, let's go with an analogy. You've made a successful forced landing in a forest clearing 100 miles from civilization, and baby, it's cold outside. The chips are down; without fire and shelter, you're going to freeze to death. Which would you rather have, a chain saw, or an ax?
__________________
Dan Horton
RV-8 SS
Barrett IO-390

Last edited by DanH : 06-11-2016 at 07:37 AM.
Reply With Quote
  #27  
Old 06-11-2016, 08:45 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 6,873
Thumbs up

Thank you Dan.
There is nothing more to say.
__________________
Any opinions expressed in this message are my own and not necessarily those of my employer.

Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #28  
Old 06-11-2016, 10:01 AM
donaziza's Avatar
donaziza donaziza is offline
 
Join Date: Jun 2007
Location: Atlanta
Posts: 466
Default

Remember note
Reply With Quote
  #29  
Old 06-12-2016, 08:45 AM
Gillegan Gillegan is offline
 
Join Date: Jul 2012
Location: Roanoke, VA
Posts: 8
Default

Just curious but has anyone ever considered using an air driven generator for backup power? They have been used in the certified world (incl. large jets) and have the advantage of no time limits.

http://www.aircraftspruce.com/menus/...ors_bpe14.html
Reply With Quote
  #30  
Old 06-12-2016, 09:42 AM
vlittle's Avatar
vlittle vlittle is offline
 
Join Date: Jan 2005
Location: Victoria, Canada
Posts: 1,912
Default

Quote:
Originally Posted by DanH View Post
The condition stated in the original question...with all electric fuel pumps and ignitions. The ability to open the master contactor without affecting engine operation is a key system test.

The KIS approach to that condition is to wire the ignitions and pumps directly to battery feeds which have no dependence on the aircraft electrical system.

Basic VFR and IFR architecture:



I'll submit three principles, often overlooked while designing grand electrical schemes with many wonderful features.

1. Any pilot should be able to operate it without instruction. Put another way, operation should be self-evident, or the same as any other airplane.

2. The battery feeds should be physically separated from the rest of the wiring, to the maximum extent possible. They should also be separated from each other.

3. The least complex system is usually the most reliable.

Humor a bit of editorializing.

Right now, we're growing a fleet with no electrical commonality. At the same time, we're bringing in more and more non-builder pilots from the traditional GA fleet. E-busses, cross feeds, and switch flipping to maintain engine noise is a recipe for increased accident numbers. Time and time again, the human factor is the stubborn cause we can't make go away.

Physical separation is important. We see a nice wiring diagram intended to isolate problems, but then the builder installs the backup alongside the primary. Doing so makes them subject to the same physical trauma, whatever it might be, and one can take out the other.

As for the least complex being the most reliable, let's go with an analogy. You've made a successful forced landing in a forest clearing 100 miles from civilization, and baby, it's cold outside. The chips are down; without fire and shelter, you're going to freeze to death. Which would you rather have, a chain saw, or an ax?
Well put. I use the VFR architecture in my Rocket. If I want to fly IFR in IMC, I would use a modified version of the IFR architecture with the two alternators, each driven from their own engine!
__________________
===========
V e r n. ====
=======
RV-9A complete
Harmon Rocket complete
S-21 in the oven
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 08:27 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.